1. Field of the Invention
The invention relates to a single- or multiple-part protective cover for traction drives such as chain, belt, toothed belt drives or the like, in particular for which engines, vehicle drives, machines or the like, having at least one inlet opening disposed in the protective cover, through which opening a gaseous medium can enter into an inner chamber containing the traction drive.
2. The Prior Art
From Examined German Patent Application DE-AS 11 42 090, it is known to surround a belt drive at least partly with a protective hood.
It is also known from Examined German Patent Application DE-AS 20 51 050 to provide a housing assembled from a multiplicity of half-shells in order to fully encapsulate traction drives, such as chain and belt drives.
From Examined German Patent Application DE-AS 11 82 008, it is known to blow cooling air generated by a fan onto pulleys in drive mechanisms.
In an apparatus for sealing an annular gap between a housing and a rotating structural component by means of a radial sealing ring having inwardly oriented sealing lips, the pressing force of which is variable with a control means by means of a fluid acting upon the sealing lips, it is also known, from German Patent 29 42 712, to make the interiors of closed housings for motor vehicle transmission system parts, for instance a variable-speed gear, a secondary drive and the front and rear axle, communicate with a source of compressed air or a vent means selectively, by means of a switch. As a result, the pressing force by the sealing lips can be temporarily increased by the imposition of compressed air, so that the sealing can be adapted to the particular operating conditions. The temporarily increased pressing force is also intended to prevent the penetration of dirt and water into the housing in the most unfavorable conditions.
Finally, it is already known from German Patent 32 01 217 to feed and vent air to and from a drive housing continuously through a ventilating device communicating with its interior; this is intended to assure that on the one hand no liquid such as rainwater or the like can penetrate the interior of the drive housing from outside, and on the other hand to assure that as little splashing oil as possible can escape to the outside.
It is moreover known for a toothed belt drive in motor vehicle engines, which substantially comprises a toothed pulley driven by a crankshaft of the vehicle, a driven toothed pulley connected to the camshaft, an idler pulley and a drive belt embodied as a toothed belt, to be shielded by means of a protective hood or cover, which is for instance secured to the front face end of the engine block.
It has been found in practice that during the operation of a toothed belt drive of this kind, especially if it is used in high-speed engines, considerable problems arise in terms of the temperature behavior and hence the strength of the belt, which is for instance made of a synthetic elastomeric material. These problems can be ascribed to the fact that where the protective cover is embodied as completely tight, i.e. as virtually a completely encapsulated housing, impacts and the like during belt operation, and in particular toothed belt operation, cause marked warming and in fact heating of this component inside the protective cover, with the attendant danger that the material comprising the belt will overheat, thus severely impairing its strength and causing it to diminish rapidly.
On the other hand, if a protective cover is provided which in order to avoid or reduce thermal problems is not completely tight, and therefore is an at least partly open housing, then the disadvantage arises that complete protection for the toothed belt drive is not assured, for instance because of the draft-creating effect of the rotating parts, and so dirt particles, rainwater, snow and the like can penetrate farther into the interior of the protective cover and thus likewise damage or even destroy the toothed belt.
A protective cover having the characteristics of the preamble to claim 1 is also known from French Patent Application 25 02 720.
It is the object of the invention to devise a protective cover that is substantially improved over the prior art as defined by French Patent Application 25 02 720, and that not only assures excellent permanent cooling of all the components of the traction drive, but moreover and at the same time assures maximum possible protection of the traction drive from impairment by dirt particles, rainwater or other foreign bodies, which precisely in the embodiment of the protective housing defined by French Patent Application 25 02 720 do after all enter through the air inlet openings of that housing to reach the interior of the protective cover, especially because of the suction exerted by the rotating parts and fan blades provided there, where they finally can damage, if not even destroy the gear parts, especially the toothed belt.